Vitamin D binding protein and the vitamin D status of Somali Women compared to a Swedish population sample

Problem

Vitamin D deficiency is common in immigrants. Whether vitamin D binding (DBP) is genetically determined or influenced by other factors is not fully understood.The aim was to study the influence of age, gender, ethnicity and effect of vitamin D treatment on DBP.

Approach

A case control study and a randomized, double blind, placebo –controlled study is performed in primary Health care unit and Sahlgrenska University Hospital, Gothenburg, Sweden. Somali women (n=102), latitude (0-10° N) residing in Sweden > 2 yrs, latitude (57° N) were compared with a random Swedish population sample of men (n=50) and women (n=231) from the WHO MONICA study.Oral drops of 800 IU, 1600 IU cholecalciferol and similar amounts of placebo were given daily for 12 weeks to the Somali women. Serum DBP and Vitamin D were monitored every 6th week and 3 months after the treatment in Somali women.

Findings

Vitamin D deficiency (S-25(OH)D <25 nmol/l) was prevalent in 73% of Somali women and in 5% of the Swedish WHO population sample. DBP was lower in Somali women than in the WHO population women (p<0.0001). DBP did not differ between men and women in the population sample and did not correlate with age, gender, body weight or bone mineral density. A positive correlation between DBP and S-25(OH)D was observed in the WHO population women only (p<0.019). DBP in Somali women was unaffected by vitamin D treatment.

Consequences

DBP was determined by vitamin D status but was independent of age, gender, ethnicity per se and vitamin D treatment. The latter could be due to suboptimal vitamin D doses given and/or the brief intervention time.